That's true. There is no standard way to accomplish that in the current stable version (neither beta, nor dev branches).

Those are two different concepts:

Newsletters use get_colored_login which currently supports $login$ and $avatar$ only, and doesn't produce a link as its output, just the image and text.

The tag User::get_identity_link() implements many other placeholders to be displayed within a link to the user's profile page.

In short, maybe we can find a way to somehow merge both features to let insert any of the user related tags into emails. Also, this thread may let us to open up the scope into new concepts, like general use tags or so, to retrieve info from posts, files, etc. and not only from users. I will cut it off at this point, just to not mix things, think a bit more about it and discuss using our regular channels. However, ideas about what I just said are welcome, of course.